| 川东-武陵构造带下古生界海相页岩构造变形特征及对页岩气保存的影响 |
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| 引用本文： | 李春麟,李小诗,王宗秀,梁明亮,张凯逊,谭元隆,陶涛,高莉.川东-武陵构造带下古生界海相页岩构造变形特征及对页岩气保存的影响[J].地质力学学报,2020,26(6):819-829. |
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| 作者姓名： | 李春麟 李小诗 王宗秀 梁明亮 张凯逊 谭元隆 陶涛 高莉 |
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| 作者单位： | 1.中国地质科学院地质力学研究所, 北京 100081 |
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| 基金项目： | 中国地质调查局地质调查项目（DD20160183）；中国地质科学院基本科研业务费项目（JYYWF20181201） |
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| 摘 要： | 川东-武陵构造带下古生界发育的两套海相页岩层系(下寒武统牛蹄塘组和上奥陶统五峰组—下志留统龙马溪组)不仅是区域内重要的滑脱层，也是页岩气勘探开发的重点层位。通过野外详细的构造解析及室内显微观察，从宏观露头—显微尺度分析了页岩的变形特征，认为页岩至少存在两期构造变形:早期顺层向北西或南东的逆冲和晚期的切层断层作用。页岩的变形强度随着与断裂带距离的变化而发生改变，远离断裂带的地区页岩变形主要表现为近直立的微裂隙，属脆性域；靠近断裂带，页岩的变形特征逐渐表现为脆-韧性过渡，开始发育糜棱化构造；在断裂带内部，页岩强烈面理化，发育大量的糜棱化构造，属韧性域。通过氩离子抛光和扫描电镜技术，分析了变形页岩内部的孔隙演化特征，认为随着变形作用从脆性—脆-韧性过渡—韧性的转变，页岩内部的孔隙类型不仅可以发生转换，而且页岩内部孔隙的大小、分布特征也随之改变。在此基础上，进一步讨论了中国南方复杂构造区下古生界页岩变形对页岩气保存的影响，认为顺层剪切滑脱作用会改变页岩内部的孔隙体系，有利于页岩气的富集；切层的伸展或走滑剪切作用不仅会破坏先前形成的油气圈闭，而且会导致油气沿着断裂带从高势区向低势区运移，进而造成油气散失。
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| 关 键 词： | 页岩滑脱变形 页岩气富集保存 下古生界 川东-武陵构造带 |
| 收稿时间： | 2020/9/15 0:00:00 |
| 修稿时间： | 2020/11/4 0:00:00 |
Deformation characteristics of Early Paleozoic marine shale and their influence on the shale gas preservation in the eastern Sichuan-Wulingshan tectonic belt |
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| LI Chunlin,LI Xiaoshi,WANG Zongxiu,LIANG Mingliang,ZHANG Kaixun,TAN Yuanlong,TAO Tao,GAO Li.Deformation characteristics of Early Paleozoic marine shale and their influence on the shale gas preservation in the eastern Sichuan-Wulingshan tectonic belt[J].Journal of Geomechanics,2020,26(6):819-829. |
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| Authors: | LI Chunlin LI Xiaoshi WANG Zongxiu LIANG Mingliang ZHANG Kaixun TAN Yuanlong TAO Tao GAO Li |
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| Institution: | 1.Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China2.Key Lab of Shale Oil and Gas Geological Survey, Chinese Academy of Geological Sciences, Beijing 100081, China3.Key Laboratory of Petroleum Geomechanics, China Geological Survey, Beijing 100081, China4.Beijing Institute of Geological Survey, Beijing 102206, China |
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| Abstract: | Two sets of marine shale systems (the Lower Cambrian Niutitang Formation and the Upper Ordovician Wufeng-Lower Silurian Longmaxi Formations) developed in the Lower Paleozoic of the eastern Sichuan-Wuling tectonic belt are not only significant decollement zones, but also key strata for shale gas exploration and development. In this paper, through detailed field structural analysis (macroscopic scale) and indoor microscopic observation (microscopic scale), it is considered that there are at least two stages of structural deformation developed in shale: top-to-the-NW/SE thrusting (D1) and the faults cutting through the bedding (D2). The deformation and strength characteristics of shale are related to the change of distance from the regional fault zones. The deformation characteristics of shale far away from the fault zone are mainly manifested as nearly vertical microcracks, belonging to the brittle domain; near the fault zone, the deformation characteristics of shale gradually show brittle-to-ductile transition and the development of mylonitization structures; within the fault zone, strongly foliated and mylonitization structures developed in the shale indicating the deformation of shale belongs to the ductile domain. By means of ion-milled backscatter SEM, the pore-structure evolution characteristics of deformed shale were analyzed. The result showed that not only the pore types in shale can be transformed, the size and distribution characteristics of pores can also change with the deformation strength. On this basis, the influence of Lower Paleozoic shale deformation on shale gas preservation in the complex structural area of South China is further discussed. It is suggested that the D1 can change the pore system developed in the shale, which is conducive to shale gas enrichment. The extension or strike-slip shearing (D2) can not only destroy the oil and gas traps formed previously, but also cause oil and gas migration from the high potential zone to the low potential zone along the fault zone, thus leading to oil and gas loss. |
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| Keywords: | shale decollement deformation enrichment and preservation of shale gas Lower Paleozoic eastern Sichuan-Wulingshan tectonic belt |
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